The field of the invention is that of large rotating machines, often having a substantially horizontal axis, such as those found in the chemical, mineral or sugar industries and provided with a large ring gear that allows them to be rotated via a pinion and a motor unit. Examples of rotating machines of this type include rotary furnaces, ball mills, horizontal pebble mills, sugar refinery diffusers . . . .
With these machines, the repeated contact between the teeth of the pinion and of the ring gear is a source of wear, which can manifest itself in various ways given the adjustment of relative position between the drive system that comprises the pinion and the driven machine, and the various movements of the machine other than the rotation about the axis. The shape of the teeth deviates from the original profile that was of the epicyclic type, their thickness decreases, and local surface defects can form.
When the contact surfaces deviate from the ideal profile, the forces exerted on the teeth can take on abnormal directions, and vibrations can occur. This leads to abnormal mechanical stresses on the attachment of the ring gear, on the motor unit, and on the machine itself and its supports that can lead to damage to the various mechanical systems and also amplify the phenomena of wear of the teeth.
When the wear reaches a significant level, the ring gear must be repaired or replaced. The operation of replacement is long and costly for large machines. Given that the rotating machine and the ring gear only rotate in one direction, the contact of the pinion on the ring gear only occurs on one of the two sides of each tooth of the ring gear. Turning the ring gear over, with the goal of exposing the other sides of the teeth that have not undergone wear, is sometimes an alternative. This operation of turning over remains, however, an onerous operation, even if it is a little less costly. In general, it is possible to carry out a repair, in order to restore a shape quality of the contact surfaces that is compatible with good mechanical operation, at least once before having to turn over or replace the ring gear.
Such a repair is carried out without disassembling the ring gear; only the protective parts are removed in order to allow access to the teeth. It consists of machining, generally via grinding, that recreates a shape suitable for meshing on a face of each tooth of the ring gear.
Today, the operations of repairing surfaces of teeth are carried out manually by operators who manipulate the machining or grinding tools. The result of the operation for each tooth is evaluated via comparison to a template that forms the reference shape.
In the experience of the applicant, the final result depends largely on the expertise and the experience of the operator.